<template>
  <div>
    <router-link tag="div" to="/" class="iconfont header-abs" v-show="showAbs">
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
      <router-link tag="div" to="/" class="iconfont">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>景点详情
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',

  data() {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  activated() {
    // 滚动监听
    window.addEventListener('scroll', this.handleScroll)
  },
  // keepalive页面即将隐藏的时候执行
  deactivated() {
    // window.removeEventListener('scroll', this.handleScroll)
  },
  methods: {
    // 滚动监听 渐隐渐现效果
    handleScroll() {
      const top = document.documentElement.scrollTop
      if (top > 20) {
        let opacity = top / 160
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = { opacity }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
      // console.log(document.documentElement.scrollTop)
    }
  }
}
</script>
<style lang="stylus" scoped>
@import '~styles/varibles.styl';

.header-abs {
  position: absolute;
  left: 0.2rem;
  top: 0.2rem;
  width: 0.64rem;
  height: 0.64rem;
  border-radius: 0.32rem;
  text-align: center;
  line-height: 0.64rem;
  background: rgba(0, 0, 0, 0.5);

  .header-abs-back {
    color: #fff;
    font-size: 0.36rem;
  }
}

.header-fixed {
  z-index: 2;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  // overflow: hidden;
  height: $headerHeight;
  line-height: $headerHeight;
  text-align: center;
  color: #fff;
  background: $bgColor;
  font-size: 0.32rem;

  .header-fixed-back {
    position: absolute;
    left: 0.2rem;
    top: 0.2rem;
    width: 0.64rem;
    height: 0.64rem;
    text-align: center;
    line-height: 0.64rem;
    font-size: 0.36rem;
    color: #fff;
  }
}
</style>
